This invention relates to a system for generating daughter radioisotopes, and more particularly to an apparatus and method for the production of daughter radioisotopes from solutions containing mixtures of parent radioisotopes and daughter radioisotopes.
Radioisotopes are commonly used for research, treatment and diagnosis in the field of nuclear medicine. Such applications include liver, lung, bone and tumor scanning. Other applications are radiotherapeutic. Radioisotopes are also used in industrial environments for process control, radiometric chemistry and the like. It is desirable to generate daughter radioisotopes with a minimum of metallic, organic and other impurities for such industrial, diagnostic and radiotherapeutic purposes.
Radioisotope generator systems for applications in the field of nuclear medicine should provide convenient on-site production of short-lived daughter radioisotopes with a high specific activity. It is desirable to produce a daughter radioisotope in high yield and minimize breakthrough, i.e. contamination with the parent radioisotope. Other contaminants such as organic radiolysis products and metal ions should also be avoided.
Parent/daughter systems employed or investigated in connection with nuclear medicine include Mo-99/Tc-99m, Sr-90/Y-90, Ge-68/Ga-68, and Ca-47/Sc-47 among others.
One currently available method of producing daughter radioisotopes from parent/daughter solutions employs ion exchange resin such as Dowex 50. The organic columns of such systems, however, are subject to radiation damage. Therefore such generator systems suffer from short usable life, limited scale-up potential, and possible contamination of the daughter product with organic radiolysis product.
Various solvent extraction methods are also used to produce daughter radioisotopes. Disadvantageously, though, solvent extraction methods are complicated and typically produce volumes of liquid organic waste contaminated with the parent radioisotope. Due to the employment of strong chelating agents, solvent extraction methods can result in daughter product solutions contaminated with extraneous metal ions from reagents and other sources.
It is also known to generate daughter radioisotopes in systems based on alumina or stannic oxide columns. A major disadvantage of such systems, though, is the potential leaching of metal ions from the metallic oxide column during acid-elution of the daughter product from the column. The presence of metal ions in the daughter product solution compromises the quality of the solution and can render it worthless.
Accordingly, a need has existed for a method and apparatus for the environmentally-safe generation of daughter radioisotopes which provide convenient on-site production of short-lived daughter radioisotopes with a high specific activity. The need for such a method and apparatus has existed which results in a daughter radioisotope in high yield with a minimum of breakthrough of the parent radioisotope whereby the potential for metallic, organic or other contamination in the daughter product is minimized.